Happy that you, family, and dogs are OK. Careful with the Ozone machine. Ozone is great for getting rid of smells. Not good for people. Don't be living in a building with a ozone machine.

Think we electric bicycle builders need to take a few steps back and think about what we are doing. Way too many fires!LiPo fires and LiPo safety issues, Thread index
Take a lesson from the power tool and electric car manufacturers. Two words that freak me out are battery and bag. Anyone who puts a battery in a cloth bag should have his head examined. Anyone who sells a battery bag should really have his head examined. I have strong feelings that lithium batteries need to be enclosed in a sturdy plastic or metal case. Ideally inside the frame. Think about vibrations, crashes, bicycle tipping over. We need more fuses and all the safety stuff that the power tool and electric car companies use.

When it comes to batteries. Lowest cost might have the highest chance of fire.

Damn Dan! I am glad you are ok and you survived this. Sorry I am late to this thread my computer went kaput. I consider you a really good friend as we have ridden together several times and I will never forget driving to Tucson with you for the Death Race. If you want to hang out still for anything give me a call anytime. I still have your old number, but you can always pm me here on the sphere.

Sorry to read this news DD. And am glad to see its all working out OK.

You were key in helping build my first ebike when I first asked for help on this ES forum years ago and improving it later, and I still haven't forgotten.

One question I have about your battery pack charging setup, was the pack in a frame bag or a saddle bag? Just can't help but wonder about the detail even though I know it doesn't make a difference.

I know you don't need to be told anything about batteries but to those who want to believe 18650s are safer than other cells you're putting yourself in a dangerous situation.
When I built my first 18650 pack with Samsung 29E cells I ordered them in separate sets, one order came ripped apart and the remains of the package had been put in an official Australia post bag with printed words along the lines "Your package has been repackaged due to extreme damage, blah, blah.."

Anyway one of the Samsung 29E cells was quite deformed, it looked like it had been run over multiple times with a forklift.
For the purpose of experimentation, I added it as the very last cell to my 18650 pack and about 1 minute later I heard a hiss, because I had just put the whole pack in a fire resistant bag I just grabbed the bag and ran outside (it was night time) and turn the bag upside down. The deformed Samsung 18650 29E cell fell out of the bag, it had melted out of the 18650 plastic cell holders like a knife through butter.

In low light/nightime, I watched the single 18650 slightly expand and then hiss more while its light blue plastic wrapping sleeve shriveled and melted away and then it fully started glowing orange just like a super hot bead of coal on fire and the flat negative terminal side bulged out round/mound shape.
It was just awesomely glowing orange hot, there are no words to describe how "pissed off" equivalent that cell was. The thing for everyone to take note of here is that unless you think you can stop something that glows orange for 15 seconds straight from not combusting other cells or materials next to the cell then you should be prepared for a fire.

Here is the cell.

Deformed Samsung 29E cell, all deformation either happened while in delivery or from its heat self expanding and glowing orange.

IMAG0149.jpg (70.72 KiB) Viewed 2041 times

Thinking back now it wasn't that different from the Terminator 3 scene where the battery glows orange and then explodes except my cell glowed orange for longer and it even did giggle a bit as the gasses excaped but there was no explosion at the end, just massive heat. https://youtu.be/X8J7VYbuplI?t=7s

The bike was built to fit the battery, in the front saddlebags. Nice tight fit, cushioned underneath, It never required any strap to hold it down tight. It did not rattle around in there like is sometimes the case with bags or looser fit boxes.

This battery was a blue shrink wrap 48v 20 ah. On arrival, it was in good shape, no indications of damage, the box looked intact, no electrolyte stink. The pack was then enclosed in a coroplast box, to protect mostly against chafing in the battery bag/ saddle bag. The battery was never dropped, nor the bike crashed. NO reason to suspect a crushed cell in there, or shorted nickel strips. But a short could have been the cause, nothing is ruled out here. It could have slowly developed a rub between a + strip, and the - can, and rubbed through the cells shrink wrap.

After about a weeks light use, as balanced as I could get it, a discharge test produced around 18 ah, so presumably some cells inside were not up to snuff somehow.

Discharging, the rate was usually about .5c on a pack supposedly rated for 3-4c. I did put it on a 40 amps bike once as a test, and saw it could not do 2c very comfy, so I never put it on a controller stronger than 22 amps after that. With 20" wheel and the slow DD motor on that bike, it was very seldom that you saw more than 800w being pulled, even towing a trailer uphill, it just would not do 1000w continuous.

About half the time, including the discharge that day, the pack was paralleled with a 13 ah allcell pack, which also sagged like grannies tits under 2c. So lots of the discharge was 800w from a 33 ah combined pack. Typically, cycles were about 15 to 20 ah from the combined packs, or 10 ah from the single 20 ah.

The packs were never charged parallel. Always each one charged separately. If in a rush, I had two chargers. The packs were never connected paralell except when both were full, at 54.6v.

That day though,, both packs were run till the bms popped, for my spring capacity test. Each spring I do this, so I can plan a very long summer ride based on current capacity. I think perhaps the bms did allow one cell group to go below spec voltage. Then when it got full charging, a damaged cell went runaway.

The other just as likely cause, the bms or the charger or both allowed an overcharge of a normal cell. No way to tell which happened, there was no trace of the bms left after the fire. The bms was in a plastic case/ box, did this cause the bms to overheat and fail? who knows, the plastic box never got scorched or melted deformed. Never should have gotten that hot, even when in balance mode. But I do wonder if the balancers were still, or even ever, working. I had not checked individual cell group voltages since it was new, you had to open the box to get at the bms plug.

So in summary, other than it was a bargain pack from alibabba, nothing in this batteries history would make you suspect it was going to flame on recharge. There was not a loss of capacity from when it was new beyond normal, it was only 1.5 years old, it was seldom run lower than 75% Dod, it was not dropped, crashed, or rattled around dirt riding, or discharged at high rates. I did not heat this pack up each ride ( So the coroplast box did not cause it to get hotter), did not series connect it.

NO reason to think it would flame. BUT IT WAS VERY STUPID TO CHARGE IT SO CLOSE TO FLAMABLE SHIT.

Interesting read. sec 4.3 was not the problem in this case. I was very careful about the operating window of the cheap ass cells. It generally pulled about .5c continuous, 18 mph top speed on that bike.

But section 4.1 might be the real reason the pack flamed, just good ol contaminated cell grew dendrites. And finally grew them big enough, that day I discharged it 100%.

For some reason, I hadn't considered that problem, since they were 18650's, and supposedly less likely to spontaneously combust. Vs a HK lipo cell, notorious for puffing and more (?) likely to flame if internally shorted.

But the fact remains, it went off just about the time it would have been full. About 4 hours after I started it charging. So maybe it simply overcharged a cell, if the bms failed to stop a group from over charging. Maybe it was shorted by a dendrite during the deep discharge ride, and it just got hotter and hotter all afternoon, and the charger just kept trying to fill it till she blew that cell. Maybe one cell was just badly made, contaminated and puffed all along, since I never got the full 20 ah from this pack from day one. I just figured from the first that all the cells put out less than claimed by the manufacturer. No name cells inside.

That night, I'd intended to charge it half way to three quarters, and stop it after dinner time. Forgot about it and went to bed. The next day was not supposed to be warm, so I wasn't planning another ride soon.

Again, the big mistakes I made were the following.

Charged in a shitty, highly flammable location. Foam seat of the motorcycle damn near touching the battery bag of the bike.

Blindly trusted a batterys bms, and chemistry, to be absolutely safe. I NEVER took a hard look at each string of cells, watching voltage of each string of cells as it charged. This should not be something you have to do,, I'm not saying you should be a battery tech to use an e bike. But I trusted it so much, and so blindly, that I chose to charge in such a shitty place.

Thinking back, how did I get so stupid with this battery? Hell, I charge all my NiCad or lithium drill batteries on a tile topped table, and have done so for decades. Never had one go off, but still I don't put those on a pile of old newspapers and charge. But this bike, I may have well as piled cans of gas on top of it, and put it on charge. Really dumb.

2 feet of space around the bike and it would have smoked out the garage, but not burned the house down. Quick action with a garden hose would not have put out the battery, but it would have cooled off the room before it could backdraft. As it was, it was already flashing over when I got out the door to try to do anything, That motorcycle seat had set the whole room on fire that quick. Just like the burning couch fire tests you see on Y tube.

As I understand it, the new DOT rules on batteries require the battery assembler to do testing to insure the cells are not counterfeit -- that they match the manufacturer's specs and performance ratings. Otherwise the battery isn't legal to be shipped. Clone cells may be ok, or may not be, you just never know. As a buyer of batteries, we don't really have access to the individual cells to do the testing. We must work with battery suppliers who are trustworthy to do it properly, and pay more for our batteries.

A lot of chargers don't shut off when they are done, they indicate charge completion when the current drops below a few percent of full charge current, and they continue to output the proper voltage to allow the BMS to balance. The BMS manages things from there. It is up to the charger to put out the correct voltage, and it is up to the BMS to disconnect from charging if any cell group gets too high in voltage.

If the charger puts out the right voltage, and the cells are balanced, they will divide the voltage and none will overcharge. The BMS in this case has nothing to do. The current will keep going down and down approaching zero. This is how power supply based bulk charging works with properly balanced cells. In order to have a problem one of two things must occur - either the supply voltage goes too high (a failure of the supply), or the cells get out of balance - only then can cell groups get too high in voltage. And with modern cells, it takes quite a lot of extra voltage to cause failure.

Lithium dendrite failures I haven't seen much about. In a high power cell, dendrites would tend to self-clear, I would think, but that's speculation.

The BMS has a very important job to do, but we have no simple way to know if it is working properly. It is frustrating they don't even provide a connector to monitor the cells. The BMS's in this price range are unlikely to be doing any self checking at all. So the BMS itself doesn't know if it has a problem. A broken BMS can easily cause unbalance and fail to stop charging, causing the resulting fire.

We need better BMS's. Actually there are better ones out there, but the price of the battery is affected by the BMS cost and this drives quality. So who can use a better BMS and still be competitive on battery pricing? The market pushes them toward the lowest cost, both in cells and BMS.

So we need battery vendors that will use good cells, perform the necessary testing, and use a quality BMS, among other things like packaging the cells appropriately and using appropriately low impedance interconnects.

I would add that they should provide a cell voltage monitoring connector so that an expert can diagnose problems without disassembly of a pack.

In the interim, put a smoke alarm or two immediately above the charging area, and have a good safe distance to nearby fuel. Campfires require a 10 foot circle free of flammable materials, for example.

I don't know, but make it a vented box otherwise its just a bigger can when it goes pop. I'm thinking about stuff like an ammo box, with a motorcycle like exhaust pipe on it. The idea is to let gasses cool before exiting the pipe.

FWIW, a contained battery such as a shark pack, or rack pack in aluminum box will pop the end off if it goes off, so that would work too, to prevent making a ---- of your battery.

Maybe a waste of weight, in the future no large batteries will be in my house. I'm going to the battery bunker in the yard. But I have thought some about what would happen if a battery fire happens while out riding. So the next custom bike I build will have metal battery boxes made from vented ammo cans at least. Buy me some time at least.

May be too peripheral for this thread, but the major e-bike manufacturers (Haibike, Specialized...) seem to have resolved this issue as I've not heard of a problem with them. Is it just better design/components?

Wow what a story! Not going to charge my battery and go to sleep any more. One of my best experiences in the ebike industry has been dealing with a man that you mention in this story. Jason Kraft has a reputation of being a stand up guy and his actions mention here confirm my thoughts. (Ebikekit)

2old wrote:May be too peripheral for this thread, but the major e-bike manufacturers (Haibike, Specialized...) seem to have resolved this issue as I've not heard of a problem with them. Is it just better design/components?

Yup, they are insured and bonded so they spend tons of cash on designing safe setups, just like power tool batteries (Makita, Dewalt) and Computer Industry (Laptops). Some battery purchased off ebay/alibaba/aliexpress has nothing. Now you buy from Justin at www.ebikes.ca its a very safe bet and guarunteed that he is fully insured and bonded, that is why the batteries are so expensive, about $60/Ah in the 36V and 48V range. Justin sells Allcell plus his own in house battery, LiGo made for transport on aeroplanes to conform to the strict laws. Of course if we had lots of money, this is a reasonable route to go. Now I do not know if they would be willing to make a custom sized battery or not. There are other vendors out there that may or may not be covered legally. Luna Cycle sells battery packs, SuPower, Greentime, yeah those are all that come to mind off the top of my head. Remember I stated MAY or MAY NOT be covered.

I will have to look into EBIKEKIT, I've read(heard) it mentioned a few times in various other threads.

I wouldnt put my trust into some random battery purchase. Dogman Dan knew what he bought though, its just a shame what happened. Luckily thats all that happened, could of been worse.

We will never know if it was the BMS or perhaps a connection or cell. But the bet is on the BMS for sure.
I hope Justin at ebikes.ca will sell some top quality BMS'
I know he custom made/designed some for his LiGo batteries.

FWIW, E-Bikekit.com has never had a battery they sold catch fire. The batteries Jason sells are UN38.3 certified so he can ship them without breaking US hazmat shipping law.

The battery that burned my house was Ali Express, not UN certified, and was shipped to me illegally. (by air, labeled power supply)

My guess is the fire was caused by overcharging of one cell group that had a weak cell, which resulted after a 100% discharge. Why that group overcharged could be for multiple reasons. The group may have had the bms fail to stop it from over discharge, followed by normal charging, or the bms may have failed to shut off an overcharge, or the group may have simply gone into thermal runaway while not yet fully charged.

But it could be the problem was even simpler, just a strip chafing into the shrink on a cell, shorting it out. That's how you make a pack blow, short it out externally of the cans.

Again, the spooky thing here is the pack showed zero symptoms of a problem. Nor was it dropped, discharged at high rate, or anything harsh. If it had showed any signs of deterioration, I would never have charged it in the garage. The ride before it went up was the spring test of capacity, which was as normal for that battery since new.

But it never did, even new, put out more than 18 ah, of 20 spec. So I knew there was poor cells in there, and kept discharge rates low.

Dogman did you keep track regularly of your cells voltage? Not just the pack voltage.

Could you say that all cells were balanced and not group were suffering significant sag under load or discharge?

I believe just tracking the pack voltage is like checking the size of an iceberg from its tips.

What matter are the cells voltage and sag, not the pack.
- if you have 1 group of cells which is significantly lower voltage than others. Its bad news... and its a time bomb you may not see from the pack voltage.
- if you have 1 group of cell sagging significantly more under charge or discharge... it's another time bomb hidden from the pack voltage

These are what matter. And better know that regularly. I believe check these once every week is all you need.

I went through my battery inventory today and found I had just left my new 58v 18650 li ion powered trimmer right next to gas cans in the barn. Running late to a dinner party and just dropped it there a few days before. Needless to say, I moved it to a spot that was surrounded by metal objects until I can make a safe spot for it to stay. I am looking at finding a better storage place for the 18v power tool packs now also because of this thread. Been Much to casual about where I have them piled now and what gets accumulated around them. Thanks for sharing the story.

The pack was never dropped or damaged. It was boxed up in a protective coroplast cover, with rubber on the bottom of the box.

Since it was fairly new, and working ok, I never tore it apart to inspect tabs or add jst plugs to monitor at cell level. I was planning to add those this spring, because the pack was going into its second summer.

It did come up short in capacity, but that was no surprise given the cheap cells, and it showed that in sag under load as well. So I babied it, giving it never more than 1c load intermittent,( except for initial testing) and generally about .5c continuous. But it did not come in 5 ah under, which would have made me very sure there was actual dead cells in there. But maybe there was, just one dead cell in there that finally blew. Or, one cell just had a poor connection.
No way to ever know.